Method and apparatus for detecting positions of center points of circular patterns

Abstract

Voting of coordinates of each pixel in a photographic image onto a Hough space corresponding to annuluses is performed, the Hough space being defined by a coordinate system having an X coordinate axis for a circle center point, a Y coordinate axis for a circle center point, and an r coordinate axis for a radial direction. A vote value of each voting position having coordinates (X, Y, r) on the Hough space is acquired as a first integrated vote value from a calculation of a number of votes given to each voting position. A position represented by (X, Y) coordinate values of a voting position associated with the largest first integrated vote value is detected as the position of the center point of the circular pattern.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a method and apparatus for detecting a position of a center point of a circular pattern, such as a pupil pattern, from a digital photographic image. This invention also relates to a computer program for causing a computer to execute the method of detecting a position of a center point of a circular pattern.

[0003] 2. Description of the Related Art

[0004] Operations for detecting positions of center points of circular patterns from digital photographic images have heretofore been performed in various fields, such as detection of positions of center points of circular patterns of circular mechanical parts and detection of positions of center points of pupil patterns in photographic images of faces. Heretofore, various techniques, such as template matching techniques and Hough transform techniques, have been utilized for detecting circular patterns from digital photographic images of objects. ...

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